Titan Sub | carbon fiber - detailed tour

Can you guess what this curious looking device  had to do with the Titan submersible? I have a high detail model to answer this question  and illustrate the finer intricacies of   this flawed but remarkable craft, which  imploded on its way to the Titanic wreck,   claiming the lives of all 5 on board including  its creator. In the media coverage carbon fiber   was made out to be the boogeyman when in reality  it is one of the strongest materials known to man. I will explain how I suspect it failed and  reverse some of the myth around carbon composite,   so you can come away from this video  better able to make up your own mind. Titan made the big jump to 5 occupants  while being significantly lighter and   smaller than anything before. Previously  only 2 or 3 could dive at a time together   to see the Titanic or do any deep diving.  The pivoting front pressure dome was the   door and made getting in and out much easier.  Other submersibles involve awkwardly climbing   down through a small hatch. The inside  diameter was just 4' 4" or 1.3m and was   lined with perforated plate. Everyone sat on  the floor on a mat. This was the ON button. The left screen displayed the sonar and on  the right was the maneuvering control display.   Steering was done with a now infamous game  controller. The rear panel closed off the aft pressure dome. On the door was a display from the camera feeds. Behind the door was equipment which had to be kept dry and at normal air pressure. We will come back for a better look. Below the floor were 4 large oxygen cylinders enough for 4 days and in between them were batteries. Passengers could stow small items below the floor. The toilet doubled as the seat at the porthole, behind a privacy curtain. It was basically a box to keep the plastic bottles and bags. Condensation formed on the inside surfaces that were cold from the freezing ocean and would slosh around at the bottom.  It would pour out when the door was reopened. Bolts on the outside sealed in the crew they could only be freed again with assistance from the outside. Subs have the nifty ability to hover in place. They do this by being at neutral buoyancy where they neither sink nor float. On the landing skids were half round lead weights  for fine-tuning the neutral flotation. Before each dive all crew were weighed with everything they were taking on board. By adding or removing weights the support crew set the neutral buoyancy just right. Slung under the hull was the drop weight system. It controlled how Titan got down and back up again. It was a simple system using ordinary heavy steel pipes held in the drop weight frame. Titan descended unpowered down to the wreck. This was possible by carrying weightsto sink. Once they reached the ocean floor the 2 weights for the downward Journey would be dropped and the sub would be at neutral flotation. The thrusters on the outside of the sub would maneuver it around to explore. The top thrusters were for up and down. The side ones for back and forward and turning. Once they were done exploring the wreck more ballast pipes would be dropped and they would float back up to the surface. The weight drop system had multiple fail-safes. If  those didn't work the crew could roll the sub to   one side and then to the other so the pipes fell  out the sides of the frame. The sub would surface   again by flotation from dropping weight. No power  was needed for vertical travel. You might think the outside shell was where the water stopped and there was air on the other side. This is easily confused but the outside coverings were there to enclose the equipment and improve streamlining.   Without them it becomes clear their purpose was  more cosmetic. The water to air boundary was the   pressure hull, the thick and extremely robust  structure which resisted the crushing water   pressure. The end domes were titanium, a light but  very strong metal. It was the center tube that was made of carbon fiber. Slicing into the pressure vessel we get to see inside the all important air pocket. The crew compartment remained at normal  atmospheric pressure during the dive. Everything outside was underwater in the ocean. Here again you see how the oxygen and batteries fitted below the floor and everything had carefully allocated places. In the aft hemisphere was the essential equipment that could not be underwater and had to  be at regular pressure. Oxygen was delivered to the passenger compartment via the regulator. The floating ball provided visual confirmation that the oxygen was flowing. The plastic box with a fan on top was the carbon dioxide scrubber. It contained soda lime pellets which removed the  excess CO2 exhaled by the humans aboard. They turned purple to indicate when they needed to be replaced after they were done absorbing carbon dioxide. As backup there were lithium hydroxide  cloths on board that could act as scrubbers.   The passengers would have a safe breathable  air environment for as long as fresh oxygen flowed and the carbon dioxide was removed. The cabling needed to get outside without leaks. This was achieved with these hull glands which had  special connector plugs on each end. They were drilled through the titanium connector ring. The tail section was outside the main hull and wet.   All this equipment was constructed to survive  the pressure the large batteries for propulsion   and spotlights were here. Above them were twin  control pods. Inside these strange orange covers   were glass domes filled with oil. These devices  were for stability control and navigation. At the back was buoyancy foam to balance the weight of the batteries and equipment. The salvaged tail assembly remained relatively intact despite the violence of the implosion. It was outside the crush zone so was spared the main force. But the control spheres were missing and the fairings ripped off. The porthole was the largest one sent to such depth so it could allow 2 people to look through at the same time. The water pressure cannot be overemphasized and the force on just the porthole alone was an unbelievable 2,700 tons.  Just imagine the weight of 450 elephants bearing down on this window. Acrylic is the favorite material for sub windows. This demonstration gives you some sense of how incredible the crush of the ocean was down at the Titanic. Why was this a carbon composite hybrid and  not the traditional all-titanium pressure vessel?  Using carbon shaved off about 7 tons of weight and enabled it to be much more compact.    A titanium center tube would have added an extra  3.3 tons and needed another 3 tons of special   syntactic foam to offset the steel weight and  maintain neutral buoyancy. The extra size and weight would have made it much bulkier and less agile requiring even bigger batteries   and heavier frame inevitably upping the weight  of the other components too. Ballooning the total weight to a hefty 17 tons instead Titan could be a lean 10 tons. And a lighter sub meant a smaller support ship which is the big expense.  The hybrid solution offered major benefits and   held the promise of redefining the possibilities  of submersible technology. James Cameron made a blanket statement about carbon fiber being wrong for this application and not meant for the serious stuff  You don't use composites for vessels that  are seeing external pressure. A conventional application would be like on an airplane and the material is under tension but in a submersible it is under pressure the exact opposite force. Carbon fiber composites aren't really known for their compressive strength. They work best in  tension. And pretty soon it became accepted fact. As we all know carbon fiber is again very strong  in tension pulling it apart but rather weak in compression. This is just plainly wrong! Carbon  fiber has exceptional compressive capability exceeding that of most steels. However tapping into this remarkable strength doesn't come easily and requires meticulous precision in the layup process. This composite Airbus wing withstands incredible compressive loads not to mention how it carries the immense engine thrust forces to the fuselage. Titan went through 2 versions of carbon  composite mid body tube. OceanGate CEO Stockton Rush describes the evolution. The carbon fiber. This is the mandrel. This thing is inch and a half thick. Filaments were laid down in alternating hoop and axial layers. We'd wind a layer and then we do a longitudinal prepreg carbon fiber lay on top and built it up to 5 inches thick. I took it to 4,000 meters and it made a lot of noise which is a very sphincter tightening experience. Sub owner Karl Stanley was on the 2nd dive. Every 3 to 4 minutes there was loud gunshot like noises. It's a heck of a sound to hear when you're that far  under the ocean. And it wasn't getting quieter on the 2nd dive. It should have been dramatically quieter. So we scrapped it. We went back. We built other one. We went to aerospace quality. We used the same prepeg that's used on the 787. So what was wrong with the tubes. Carbon fiber had the necessary technical strength for this application   so I suspect weaknesses in the layup process.  3/4 of the water pressure acts onto the face of the tube The hoop arrangement of fibers carries this massive compression force. They were more   than capable of handling the load with a generous  safety factor. They are few materials capable of   these stresses. A quarter of the force on the hull  was from the pressure on the end domes squashing   them together and the axial fibers carried this  load. This is likely where the problem lay. The geometry of the mandrel meant no tension was  applied to these fibers so kinks and wrinkles   could not be pulled out. If the layup is bad the  load capacity is just a fraction of what it should be. I suspect the crooked longitudinal fibers  progressively failed over the 13 or so deep dives.   Or uneven axial layers formed dangerous wobbles in  the hoop filaments. The 5 inch structure loses all   its strength if there was a defect lost in most of  the thickness. The 1st hull had its axial fibers   laid manually. In the 2nd version they rolled  the fibers with the robot which was better but   the mandrel was reused and the same problem of  no axial tensioning was repeated. The winding was a lengthy process and took many weeks. Only a mandrel with rounded ends could have ensured   the straight filaments throughout but this  would have required a new mandrel and meant   throwing away both round ends which would have  accounted for approximately 40% of this really expensive material.  The investigators have access to the wreckage which holds crucial   clues and will enable them to draw highly informed  conclusions as to how the sub failed. Here we see a hull gland which confirms this is the rear connector ring. Both rings were recovered. A long metal strip was dangling off the forward  ring. This was a flange from the carbon fiber   glue joint torn away in the implosion. Almost  all flanges were torn off. This is the clearest   evidence that it was the tube that failed and  not the porthole or anything else. I find it really interesting that the outer flanges were  blown outwards in the opposite direction of the implosion.  Titan represented a radical departure from established submersible design norms. So it demanded a comprehensive exploration of this  novel application of carbon fiber. The sphere was the tried and tested pressure vessel so this new capsule shape had to be proven. The unusually thick layup needed to be fully scrutinized for all its implications plus the integrity of the   titanium glue joint under these extreme pressures  had to be validated although it is important to   add the titanium and composite are regularly  bonded in aviation so the idea is not new. Only by testing to destruction could they establish  what the real-world failure pressure was and   understand the long-term fatigue performance. This  was the only way to build in enough safety margin   to make it capable of the repeated dives that  were expected from it. Hull 2 was tested once in   a pressure chamber and then sent diving without  knowing its failure depth. We tested it at the deep ocean test facility in Annapolis Maryland. An amazing facility. The only one on the planet where   you can put something like that for a test. And  then in 2021 after having to cancel twice before,   we were able to go out and dive on the  Titanic. Stockton Rush foolishly thought he could circumvent a destructive testing program  by relying on his unproven acoustic sensors to   detect the early signs of failure. But the  brittle nature of composite gives little to   zero warning and it is safe to assume the  system didn't work. It is unbelievable how   he had such confidence to dive himself and  to take others with him carbon fiber fails   suddenly like glass without warning. Together  one moment and in a thousand pieces the next. Titan failed because OceanGate did not have  the resources and commitment to perform the   rigorous and exhaustivetesting to thoroughly  research and develop this novel use case. And considering OceanGate's cavalier attitude to best practices I'm not convinced they could have successfully pulled off making an all-titanium craft either. I find it tragic that  Stockton Rush focused his boundless energy in producing a craft with a slightly wider   affordability instead of making peace with the  astronomical passenger fee which was the only   path to generating the funds to justify the huge research and development costs that were essential for guaranteeing success. Composite if properly researched and built correctly was strong enough for this application and would have opened the path to lighter and much more compact and nimble submersibles. Another cruel myth is the fake transcript which fed the terrifying notion that the crew knew they were in peril for 19 minutes. Many clues prove that is nonsense such as escending with the thrusters which is not the the way it worked. It is for the investigators to determine for certain  what happened and why it failed and I look forward to their findings. I value the credibility of my channel and so accuracy is important. Corrections are welcomed and so is any inside information. I hope you found this useful and if you did be sure to like and subscribe. Thank you for watching  till the end and I will see you next time.

Channel: Mike Bell

Views: 393,771

Keywords: Jeffostroff, Aitelly, Real Engineering

Id: UO4IKYXacvM

Length: 16min 32sec (992 seconds)

Published: Tue Oct 10 2023